In an electroluminescence (EL) element, a light emitting layer is formed on a transparent substrate so as to be interposed between an anode and a cathode. When a voltage is applied between the electrodes, light is emitted by exciters generated by recombination of holes and electrons injected as carriers to the light emitting layer. EL elements are generally classified into organic EL elements in which an organic substance is used as a fluorescent substance of a light emitting layer, and inorganic EL elements in which an inorganic substance is used as a fluorescent substance of a light emitting layer. In particular, organic EL elements are capable of emitting light of high luminance with a low voltage, and various colors of emitted light are obtained therefrom depending on the types of fluorescent substances. In addition, it is easy to manufacture organic EL elements as planar light emitting panels, and thus organic EL elements are used as various display devices and backlights. Furthermore, in recent years, organic EL elements designed for high luminance have been realized, and attention has been paid to use of these organic EL elements for lighting apparatuses.
A general organic EL element has a configuration in which a transparent electrode such as ITO is formed as an anode on a glass substrate, an organic layer including a light emitting layer composed of an organic light emitting material or the like is formed on the anode, and a metallic thin film layer such as aluminum is formed as a cathode on the organic layer. The anode is present between the substrate and the organic layer, and thus, in order to connect the anode to an external power supply terminal, a portion of the anode or a portion of an auxiliary electrode which assists in the electrical conductivity of the anode is provided so as to extend to the outside of a region where the organic layer is formed, and the extended portion serves as an electrode taking-out portion. In addition, the anode, the organic layer, and the cathode excluding the electrode taking-out portion of the anode and a portion of the cathode are sealed by a sealing member such as copper foil. According to this configuration, light generated by the light emitting layer when a voltage is applied between the anode and the cathode passes through the anode and the glass substrate directly or after being reflected by the cathode, and then is taken out from the element.
Unlike a general LED (inorganic EL element) in which a light emitting layer is crystalized, an organic layer of an organic EL element which includes a light emitting layer is composed of an organic material such as a polymer and thus can have flexibility. In addition, among such organic materials, there are some materials from which a light emitting layer can be formed by spin coating, ink jet printing, screen printing, or the like in addition to vacuum deposition. Furthermore, the substrate is not limited to the above-described glass substrate, and a translucent plastic substrate having flexibility can also be used as the substrate. When these materials are used, the organic EL element can be used as a light source of a flexible light-emitting device which can be wound or folded. In addition, there is known a method for manufacturing an organic EL device by a so-called roll-to-roll process in which a flexible substrate which is wound in a roll shape is fed to a film-forming apparatus for forming a light emitting layer and the like, and a device is wound in a roll shape and collected after film formation (e.g., see Japanese Laid-Open Patent Publication No. 2010-165620.)